Underwater Welding Research Articles

Recent Developments on Underwater Welding of Metallic Material

Underwater welding is the process of connecting two similar or different metals which are carried out underwater. This process is applied in various construction of engineering materials both on land and underwater environments such as in ship construction, oil and gas mining in the middle of the sea and nuclear power plants. Material construction greatly influences the method suitable for the welding process. It will affect the evolution of the microstructure and mechanical properties of the material. So, it will affect the results of the welded joint.

Development of a hatch system for the determination of diffusible hydrogen in underwater welding

The design and implementation of hatch mechanism aims to optimize the development of welding simulations performed in the Robotic, Welding and Simulation Laboratory. The project is part of the upgrade technologies applied to sciences of the sea, and make it possible to evaluate the influence of welding parameters on SMAW and FCAW processes, especially as regards the content of diffusible hydrogen specimen welding in different depths. Due to the specifications imposed by the gas chromatography standards applied to welding, tests must be carried out at short intervals, which requires a fast process. This research will promote the evaluation of commercial electrodes and promote the development of new consumables.

Analysis of the Application of Laser Welding Technology on Maintenance of the Underwater Components of Nuclear Power Station

This paper put its eyes on the PWR’s underwater components which have the risk of early failure after long-term inservice because the material tends to deteriorate and embrittle due to irradiation and other factors, and should be maintenanced. In this paper, we contrastively analyse two main technologies used as underwater welding, named underwater wet laser welding and underwater local dry laser welding. It is difficult to obtain high quality weld seam by underwater wet laser welding for the reason of some disadvantages on laser beam underwater, such as water attenuation, bubble reflection and so on. On constract, underwater local dry laser-welding can obtain high quality weld-joints, and becomes the current hotshot. But, there are still some problems to be settled, such as the way to obtain stable underwater chamber and the protection of back of full penetration weld. Analysis of the retrieva of underwater laser welding on Web Science, we can find that underwater laser welding technology has step out laboratory to engineering application and the in-depth theoretical research is also actively carried out on the fields of picosecond, femtosecond laser.

Under water glued stud bonding fasteners for offshore structures

The installation of offshore wind turbines has achieved rapid and substantial progress worldwide and further increase is predicted by enhanced technologies that will reduce costs and increase service time. Secondary structures applied to the primary structure, as the transition piece of a monopole, can be e.g. cable support, boat landing or anode systems. These structures are often welded, which leads to problematic notch effects and hydrogen embrittlement, especially for underwater applications. Also the handling of technical equipment as power current or artificial housings for scuba divers for underwater welding is challenging. Adhesive bonding will lead to cost reduction as the mentioned negative aspects can be avoided. The corrosion protection coating and the primary structure will no longer be damaged and therefore do not need a subsequent coating. This article focuses on the area which is permanently exposed to water. A critical point is how the capability to form adhesion and cohesion, will be influenced by the application process under water. Therefore, stud bonding fasteners are designed that enable the injection of adhesive to the bonding area under water. The load capacities for different adhesives, surface pre-treatments and the degradation by exposure to artificial sea water were investigated. Adhesion was achieved with two different adhesives, which were able to cure and realize reasonable strength under water. Furthermore, two selected coating systems were able to improve the performance of the adhesive bond.

Sliding Mode Impedance Control for contact intervention of an I-AUV: Simulation and experimental validation

Position/force control of an Intervention Autonomous Underwater Vehicle (I-AUV) is essential to many underwater intervention tasks (e.g., marine equipment maintenance, underwater welding and so on), and is challenging due to unknown fluid disturbances and model uncertainties. This paper applies the Sliding Mode Impedance Control (SMIC) to the full contact intervention of an I-AUV, from non-contact phase to contact phase. Both computational simulations and practical experiments are conducted to investigate the performance of SMIC. In simulations, considering model uncertainties and detailed fluid disturbances, accurate position and force tracking can be achieved, with the position tracking errors within ±3 × 10−3m and a Root Mean Square Error (RMSE) of 4 × 10−2N in tracking the desired contact force of 10N. For the purpose of experimental validation, the SMIC is implemented on an I-AUV developed in the University of Technology Sydney (UTS). The experimental results demonstrate the SMIC’s good performance in the contact intervention of the I-AUV, with the position tracking errors within ±1.6×10−2 m and a RMSE of 0.97N in maintaining the desired contact force of 10N.

A novel underwater submerged-arc welding acquires sound quality joints for high strength marine steel

The serious interferences from the surrounding water severely limit the process stability and joint quality of the current underwater welding technologies. To effectively isolate the welding area, a mixture of epoxy resin and submerged-arc flux was innovatively prepositioned in the welding area during underwater welding process. Butt welding experiments of a typical high strength marine steel were conducted to verify the advantages of this technique. Compared with the traditional underwater wet welding, underwater submerged-arc welding significantly optimized the arc burning environment due to the covering and isolation, which effectively improved the stability of welding process. Defectless joints with microstructure that full of fine acicular ferrite and high-quality mechanical properties, especially, outstanding performance of ultimate strength and plasticity were obtained. The results are expected to positively widen the practical application of underwater welding in many water related industries.

Centroid variability model–based control of HITUWV for automatic underwater welding with enhanced stability and accuracy

This article presents a centroid variability model–based controller of HITUWV (Underwater Welding Vehicle by Harbin Institute of Technology), an underwater welding vehicle, for automatic welding with high stability and accuracy. First, an accurate centroid variability model, which considers the coefficient changes of the HITUWV caused by the movements of a 3-degree-of-freedom manipulator, is presented to perform the dynamic characteristics of the HITUWV precisely. Second, a centroid variability model–based adaptive sliding model controller is developed for the HITUWV to complete centroid variability compensation. Experimental results indicate that the proposed centroid variability model–based adaptive sliding model controller demonstrates better performances in stability and accuracy than the conventional proportional–integral–derivative controller and the model-based proportional–integral–derivative controller. As a result, the centroid variability model–based adaptive sliding model controller holds great practicality and utility on the control of underwater operation with high stability and accuracy.

About the design, development of an automated SMAW setup and the weldment analysis in air and wet working environment

The aim of this research is to design and to develop a computer controlled low-cost underwater welding setup for shielded metal arc welding (SMAW) process to work in dry as well as in wet welding conditions. Investigations of the microstructure and mechanical properties of the welded joints made from AISI 1010 steel plates using this setup, in air, tap water, and saltwater working environment, respectively, have been carried out. Weld bead geometry, microstructure, ultimate tensile strength (UTS), ductility, impact strength and Vickers microhardness of air and wet welded joints have been characterized and compared. The general weld bead size is quite dissimilar for air, tap water and salt water welded joints. The tap water and salt water welds seem to be wider with a slightly higher weld penetration with lower reinforcement. The maximum value of the the average UTS of the welded sample as per ASTM was 485.74 MPa. The experiments showed that the maximum percentage of elongation of samples welded in different conditions is 8.06 % and the maximum value of the average impact strength of 25.64 J was found in case of air welds. The microhardness value of fusion zone (FZ) was greater than base metal (BM) in all the welded samples. It was noted maximum up to 310.8 HV10 at coarse grain heat affected zone (CGHAZ) of tap water welds. The mechanical properties of the salt water welds deteriorated due to porosity, slag inclusion, undercut, increase in hydrogen and oxygen content in the welds.

Role of Bead Sequence in Underwater Welding.

This paper presents examinations of the role of the bead sequence in underwater welding. Two specimens of wet welded layers made by covered electrodes with the use of normalized S355G10+N steel were welded by a reasonable bead sequence. For each specimen, metallographic macro- and micro-scopic tests were done. Then, Vickers HV10 hardness measurements were conducted for each pad weld in the welded layer. The results show that welding in the water environment carries many problems in the stability of the welding arc, which influences the properties of the welds. The effects of refining and tempering the structure in heat-affected zones of earlier laid beads was observed, which provides a reduction of hardness. The possibility of applying two techniques while welding the layer by the wet method is described. It is stated that a reasonable bead sequence can decrease the hardness in heat-affected zones up to 40 HV10. Tempering by heat from next beads can also change the microstructure in this area by tempering martensite and can decrease susceptibility to cold cracking.

Parametric Study of Underwater Laser Welding on 304 Austenite Stainless Steel

The underwater laser welding assisted by a single-layer gas torch was carried out on the austenite stainless steel based on the underwater laser welding experimental platform. Butt welding experiments under shallow water were performed to investigate the effects of laser power, welding speed and defocusing distance on the underwater laser welding quality and optimized the process parameters. It was found that the ideal underwater laser weld can be obtained with the laser power of 2.0 kW, the welding speed of 2.0 m/min and the defocusing distance of 1 mm, demonstrating the self-developed single-layer gas-assisted drainage device could create working environment similar to onshore laser welding, by analyzing the metallographic structure and mechanical properties of underwater laser weld and in-air laser weld.

Investigation of Arc Bubble Affecting the Arc Stability and Improvement of Weld Appearances Using Bubble Constraint Device in Underwater Wet Welding

The generating, floating and collapsing of arc bubble is a special phenomenon in underwater flux-cored wet welding. The configuration changing process of bubble will change the stress on droplet and influence the droplet transfer process. In this study, the shape changing of bubble is captured in graphic and the real-time electric signal data is obtained. The impact of bubble floating and collapsing results in the globular repelled transfer mode, which also reduces the arc stability. A self-designed gas-shield cover is used as a bubble constraint device to improve the welding process stability and weld appearances by limiting the free floating and expansion of arc bubble. The relationships between the cover diameter and the characteristics of weld appearance are studied.

Dual-Task Interference Between Swimming and Verbal Memory.

A dual-task study was performed to explore the performance effects for swimming, word recall, and the combination of the two tasks performed simultaneously. Dual-task interference studies have been performed for a variety of tasks; however, there has not been much dual-task interference research where one of the tasks is a naturalistic physically strenuous task. Swimming is a unique physical task that requires spatial orientation on three dimensional axes, similar to that of flying, but has no risk of falling. Previous studies have been conducted in other activity combinations with word-free recall, such as running and climbing, but swimming has yet to be explored. A verbal memory recall task and swimming task were performed in isolated (single-task) and simultaneous conditions. A comparison of effects across these different activities was also explored. Swimming and the word-recall task resulted in significant dual-task interference: almost as much as when word recall was paired with another verbal task, but more than running and less than climbing. Consistent with other dual-task studies, this study observed dual-task interference between the physical swimming task and the cognitive verbal memory task. Future technologies and training for personnel who engage in water rescue or commercial diving, such as underwater welding and fiber optic cable, may be improved by these findings.

Control of Droplet Transition in Underwater Welding Using Pulsating Wire Feeding.

Underwater wet welding technology is widely used. Because the stability of droplet transfer in underwater wet welding is poor, the feasibility of improving the droplet transfer mode has been discussed from various technical directions. In this work, the characteristics of pulsating wire feeding were studied in the pulsating wire feeding mode by investigating the effects of changing the pulsating frequency, the wire withdrawal speed, and the wire withdrawal quantity on the droplet transfer process and the welding quality. With the aim of improving weld forming and welding stability, the authors selected the coefficient of variation and the ratio of unstable droplet transfer as the indexes to evaluate the effect of droplet transfer control. The pulsating wire feeding process of underwater wet flux-cored wire was analyzed in depth, and the following conclusions were drawn: using the pulsating wire feeding mode and after comparing and analyzing the pulsed wire feeding process under the same frequency condition, the authors found that the forming and stability were better under the conditions of slower withdrawal speed and smaller withdrawal quantity. The short-circuit transition ratio decreased steadily with the increase of pulsating wire feeding frequency, the rejection transition ratio first rose and then decreased, and the splash ratio first decreased and then rose.

Microstructure and Impact Toughness of Local-Dry Keyhole Tungsten Inert Gas Welded Joints

In this paper, the microstructure and impact toughness of a S32101 duplex stainless steel underwater local-dry keyhole tungsten inert gas welded joint were studied. The impact toughness value of the underwater weld metal reached 78% of the onshore weld metal, which is in accordance with the underwater welding standards. The proportion of austenite in the underwater weld metal was 0.9% lower than that of the onshore weld metal. The proportion of the Σ3 coincidence site lattice boundaries and random phase boundaries in the underwater weld metal, which significantly influence the impact toughness of the weld metal, were smaller than that of the onshore weld metal.

Analysis of cable force on steady-state motion of remotely operated vehicle for reaction pool underwater welding

Remotely operated vehicle is a reliable and efficient tool in routing inspection of reactor pools of nuclear power plants. While, there is still no study on steady-state motion of remotely operated vehicle which is crucial for reaction pool underwater welding reported. In practice, the cable force has been considered as a critical factor affecting the vehicle’s operation. To evaluate and predict the disturbing effect caused by the cable mounted on the tailing of a vehicle, a numerical simulation can be employed. In this work, we set up a theoretical model of a cable partially in reaction pool water and air to validate the remotely operated vehicle design and reduce the prototype developing time. We programmed the model governed by an ordinary differential equation set, which was considered as an initial value problem following a dimensionless treatment to be solved. The influence by factors (i.e. velocity, water depth, entry water angle, water density and cable length on tension, normal shear force, and binormal moment) was quantified by a numerical method. The test of a cable force was carried out to verify an authenticity of the three-dimensional mechanical model and a numerical method. The results demonstrated that the presented method could be used to evaluate the effect of real environment factors on a remotely operated vehicle steady-state motion and held a potential to improve the remotely operated vehicle design and control strategy.

Comprehensive analysis of spatter loss in wet FCAW considering interactions of bubbles, droplets and arc – Part 2: Visualization & mechanisms

Severe spatter loss in underwater wet FCAW was measured, analyzed and improved in the previous research. However, the underlying mechanisms are still not clear. Via visually sensing the complex interactions between droplets, bubbles, welding arc and surrounding water, the spatter generation process and mechanisms were comprehensively investigated. Two typical spatters in underwater welding were observed, i.e. explosive and repulsive spatters. The bubble evolution process, arc behaviours (burning, extinguishing and reigniting), and droplet transfer jointly caused the generation of spatters. Related to the droplet transfer process, the liquid metal might change into spatters when its transfer trajectory of high-temperature liquid droplet was significantly affected by the bubble necking location and timing.

A novel localization approach for underwater welding vehicles in spent fuel pools via attitude heading reference system and altimeters

In this article, a novel localization approach incorporating attitude and heading reference system and underwater altimeters is presented to accurately localize the underwater welding vehicles in spent fuel pools of the nuclear power stations. Different from the conventional underwater localization technologies, the presented localization approach is a more suitable approach in cases of confined structured water areas. Firstly, a multi-regions division localization algorithm is proposed for calculating the coordinate of the underwater welding vehicle through data from sensors. Also, considering the attitude errors of the underwater welding vehicle, the beam angle of the altimeters, and the boundary effects of cross-regions, an optimized multi-regions division localization algorithm is introduced for general applicability of the multi-regions division localization. Then, computer simulations are employed to evaluate the validity and the performance of multi-regions division localization and optimized multi-regions division localization. Finally, the efficiency of the proposed approach is confirmed via system experiments. The experimental results are consistent with simulation results which further indicate that the presented approach holds great potential in effective underwater vehicles localization for confined structured water scenarios.

Research on Welding and Processing Behavior of Electrodes and Features of their Application in "Wet" Underwater Arc Welding

Three brands of special electrodes for underwater welding were analyzed: LKI-1P, EPS-AN, UW-EZ-2. Experimental data on welding and processing behavior of these types of electrodes in the conditions of underwater arc welding were obtained: melting factor, metal deposit factor and losses. Experiments have been performed to determine the value of the arc breaking length of electrodes when welding under water. A comparative analysis was made with UONII-13/55 electrodes when welding in air conditions.

The influence of the welding environment on the properties of Tekken joints made from S355J2C+N steel

There are three main methods of underwater welding: dry, wet and intermediate between them, by using the local dry chamber. Due to low costs, the most common method is the wet welding with the use of covered electrodes. Water as a welding environment carries out a lot of problems. The first is limited visibility and instability of the welding arc. The biggest problem during underwater welding is high susceptibility to cold cracking, resulting from the increased diffusible hydrogen content in deposited metal and high stress values.In the work, Tekken joints from S355J2C+N steel were made in air and in water environment. The joints were subjected to non-destructive visual (VT) and penetrant (PT) tests. Then, macroscopic tests and hardness measurements were performed. The results confirm the literature reports that the water environment causes an in-crease in hardness in the heat affected zone (HAZ), which promotes the formation of cracks in welding joints.

Robotization of Operations in the Petroleum Industry

As the petroleum industry ventures into deep and ultra-deep waters in pursuit for increased oil production to meet the global energy demand, challenges of personnel health and safety and environmental pollution have gained a considerable amount of attention. One notable accident that has sparked this attention is the explosion of the Deepwater Horizon offshore petroleum platform that led to the spillage of oil into the water bodies. In tackling these challenges and preventing the reoccurrence of such accidents, the application of robotic automation in these environments, adjudged to be hostile and prone to high level of risk, provides the only option for safe and cost-effective operations. With the success of robotic automation in the manufacturing and aerospace industries, the oil and gas industry aim to take the advantages of increased reliability, accuracy and efficiency provided by robotics and automation technologies in improving operations and production both onshore and offshore and limiting the exposure of human workers to explosive and harsh onshore and offshore environments. In recent times, robotic technologies such as remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), underwater welding robots and teleoperated unmanned production platforms have been deployed to facilitate smooth operation and production in ultra-deep waters. Thus, this paper investigates some of the various onshore and offshore operations such as exploration, tank and pipe inspection that require automation, the application of robotics and automation technologies to these operations, and the challenges and issues (such as human-robot interaction) involved in deploying robots in a dynamic environment.